Satellite images of an Iranian military facility appear to show trucks and earth-moving vehicles at the site, indicating an attempted cleanup of radioactive traces possibly left by tests of a nuclear-weapon trigger, diplomats told The Associated Press on Wednesday.

The assertions from the diplomats, all nuclear experts accredited to the International Atomic Energy Agency, could add to the growing international pressure on Iran over its nuclear program, which Tehran insists is for peaceful purposes.

While the U.S. and the EU are backing a sanctions-heavy approach, Israel has warned that it may resort to a pre-emptive strike against Iran's nuclear facilities to prevent it from obtaining atomic weapons.

Two of the diplomats said the crews at the Parchin military site may be trying to erase evidence of tests of a small experimental neutron device used to set off a nuclear explosion. A third diplomat could not confirm that but said any attempt to trigger a so-called neutron initiator could only be in the context of trying to develop nuclear arms.